"possibility of shipwreck artifacts/coins" = zero to none.
The west coast (CA, OR, WA) was/is nothing like the gulf of mexico (ala "mel fisher" blah blah treasure coast, blah) stuff. Two big differences:
a) We did not have the shipping history of the legendary south American galleons on their way back to Europe, laden with silver and gold. Our west coast shipping is 1) short-lived compared to there, as this was the remotest ends of the world even into 1800s. and 2) our shipping is primarily industrial, fishing, commercial, etc.....
Not sloppy wooden ships filled with coins, blah blah. Thus any shipwreck here is bound to be modern trawlers, fishing vessels, commercial stuff, etc... And even if old, only stuffed with commercial raw materials, or whatever. Only a VERY SHORT few years of some gold leaving CA, by ship, during the gold rush. But soon thereafter, the safer trans-contintental RR's took over.
b) Those beaches @ FL and gulf have long shallow shelves which invited shipwrecks, and strewn the resultant targets into possible beach-side sand. But no, not at all like our west coast topography. If a ship went down a mere few hundred yards off-shore, it was/is in inpenetrably deep water. As the coast line drops off instantly to depths which are simply not "beach side sand". Hence the singular gold rush ship found out there, they had to use frickin' submarines to reach it. Sure, a few ships beached right on sand, but not carrying the type of stuff you read about @ Florida.
c) yes Spanish galleons came back from the Phillipines in the 1700s, and skirted along our coast (From SF area southward, sorry, not OR or WA). Yet they were not of the cargo of the lore of what you read of in FL. These were returning with raw good from the orient: silks, wax, spices, porcelins, etc.... NOT gold and silver. At *best* they left Mexico with that ON THEIR WAY EASTWARD from the mother country of Mexico. But their return trip that skirted the west coast, had only the raw good they bought. But again, EVEN IF you knew where one went down, you'd need a submarine to reach it, and would be rewarded with wax globs and broken porcelin. Woohoo.
Hence, your best bet is to angle for fumble finger losses like the rest of us west coast beach hunters do. Especially when winter storms/swells erode the tourist beaches and wash out the sand
